Passive subsea cooler

Abstract

A passive subsea cooler (1) comprises an inlet manifold and an outlet manifold, wherein at least one set of cooler pipes (2) are arranged between the inlet and outlet manifolds. The inlet manifold comprises at least a first inlet header pipe (3) and a second inlet header pipe (4), wherein at least one set of cooler pipes (2) is connected to the first and second inlet header pipes (3, 4), respectively, the first and second inlet header pipes (3, 4) being arranged essentially parallel to one another and essentially horizontal.

Description

[0001] PASSIVE SUBSEA COOLER

[0002] TECHNICAL FIELD

[0003] The present invention relates to a passive subsea cooler comprising an inlet manifold and an outlet manifold, wherein at least one set of cooler pipes is arranged between the inlet and outlet manifolds.

[0004] BACKGROUND

[0005] Coolers are widely recognized in various fields, such as automotive radiators and refrigeration systems. A representative example of a cooler is described in GB 2145806, which illustrates a stack of serpentine coils used in a refrigerator cooling system. Another example is provided in WO 2009 / 046566, which describes a cooling unit assembled from bends and straight sections of stainless steel. Subsea coolers are also well known, with WO 2008 / 004885 detailing a lightweight underwater cooling assembly.

[0006] It is well established that the performance of a compressor is significantly influenced by the temperature of the medium being compressed. Cooling the medium has been shown to enhance compressor efficiency. In subsea environments, this becomes particularly critical due to the remote location and challenging access to subsea installations. Efficient cooling in these conditions not only improves compressor performance but also reduces costs. Additionally, the remoteness of subsea operations demands systems that are highly reliable and capable of operating without faults for extended periods. However, cooling a hydrocarbon well stream introduces its own challenges, as such streams typically contain water. Lowering the temperature can cause water to separate out as free water, increasing the risk of hydrate formation. Therefore, it is essential that subsea cooling units are carefully designed and tailored to the specific requirements of the medium, including its composition and volume, to ensure optimal performance and reliability.

[0007] US 2012 / 0298343 A1 discloses a tailored cooling system that emphasizes the customization of the cooling unit to suit the specific composition and volume of hydrocarbon well streams. This adaptation minimizes the risks associated with hydrate formation. Also, it is designed to operate efficiently in subsea environments, where remote locations and difficult access make reliability and fault tolerance critical. By controlling the cooling process and separating water from the well stream in a controlled manner, the system reduces the likelihood of hydratesforming, which can cause blockages. The unit is engineered for extended operation without frequent maintenance, addressing the challenges posed by remote subsea installations. The use of specific materials and assembly techniques ensures the cooling unit can withstand harsh underwater conditions while maintaining performance and durability.

[0008] Further, a modular subsea cooling unit is described designed to efficiently cool hydrocarbon well streams in challenging underwater environments. The unit comprises two parallel header pipes (inlet and outlet) connected by sets of cooler coils arranged in a single plane. These coils, configured in a serpentine pattern using standard prefabricated pipes and bends, provide a continuous flow path for the medium, which is cooled externally by seawater. The design allows multiple sets of coils to be stacked or added during the unit's operational life, enabling easy customization of cooling capacity.

[0009] The system's modularity and use of standardized components ensure cost-effective manufacturing and adaptability to specific requirements, such as adjusting flow path length, pipe diameter, and coil spacing. The unit's versatility is enhanced by the ability to orient coils in various 3D configurations, while its robust construction supports long-term reliability in subsea environments. This invention provides an efficient, scalable, and easily maintainable cooling solution for remote subsea installations.

[0010] There is currently room for improvement, for instance lowering the weight of a cooling unit and / or the production efficiency.

[0011] SUMMARY

[0012] It is an object of the present invention to provide a passive subsea cooler that is lighter with maintained capacity.

[0013] According to a first aspect of the present disclosure a passive subsea cooler comprises an inlet manifold and an outlet manifold, wherein at least one set of cooler pipes are arranged between the inlet and outlet manifolds. The inlet manifold comprises at least a first inlet header pipe and a second inlet header pipe, wherein at least one set of cooler pipes is connected to the first and second inlet header pipes, respectively, the first and second inlet header pipes being arranged essentially parallel to one another and essentially horizontal.This arrangement enables the cooler pipes to be positioned in closer proximity to one another, optimizing the compactness and efficiency of the cooling unit. By using dual or multiple inlet headers, the cooler design can be made significantly more compact. Distributing the inlets across multiple headers allows for a reduction in the overall spacing between pipes, enabling a denser arrangement and a more compact design. This results in a smaller and more efficient cooler.

[0014] According to another aspect of the present disclosure the outlet manifold comprises at least a first outlet header pipe and a second outlet header pipe. To facilitate streamlined production and reduce manufacturing complexity, the inlet headers and outlet headers are preferably designed in a similar fashion, with corresponding dimensions, shapes, and specifications. This uniformity in design simplifies the production process by allowing the use of standardized materials, tools, and assembly techniques for both types of headers. By maintaining consistency in dimensions, such as pipe diameter, wall thickness, and connection points, the manufacturing process becomes more efficient, reducing the need for specialized components or custom fittings for each header. However, the number or size of the outlet headers can also vary from the inlet headers, meaning for instance that they, the outlet headers, do not necessarily have to match the number of inlet headers.

[0015] Additionally, having inlet and outlet headers constructed in a similar manner ensures ease of assembly and compatibility during the integration of the cooling unit. This approach minimizes potential errors or misalignments during production, leading to faster and more accurate construction. It also reduces inventory requirements, as the same components can be used interchangeably for both headers (inlet and outlet), lowering material costs and storage needs.

[0016] Overall, the use of similarly constructed inlet and outlet headers enhances production efficiency, lowers costs, and improves operational reliability, making it a practical and effective design strategy for subsea cooling systems.

[0017] According to yet another aspect of the present disclosure the inlet header pipes and outlet header pipes are arranged essentially parallel to one another and essentially horizontal. The subsea cooler unit with this arrangement is more compact in volume.

[0018] The at least one set of cooler pipes is arranged in one plane according to an aspect of the present disclosure. From a manufacturing perspective, this design offers significant advantages due to its simplicity and modularity. The straightforward construction reducescomplexity during production, enabling faster assembly and lower costs. Each set of cooler pipes / coils is designed as an independent unit, making the manufacturing process more standardized and scalable. This modular approach minimizes the need for intricate adjustments or customizations during fabrication, ensuring consistent quality and reliability across all units.

[0019] According to yet another aspect of the present disclosure, the at least one set of cooler pipes / coils comprises at least three straight pipe sections and at least two 180 degrees bend sections.

[0020] According to yet another aspect of the present disclosure, the at least one set of cooler pipes is constructed from a single continuous pipe. This design significantly reduces the amount of welding required, as it eliminates the need for welding connections between the straight pipe sections and the 180-degree bend sections. By forming the entire set from a single pipe, the manufacturing process becomes much more streamlined and efficient, reducing both the time and labor involved in assembly. An alternative is to have at least some straight pipe sections and 180-degree bend sections (U-bend sections) made of one single pipe to reduce the number of connections / welds as compared to prior art design.

[0021] Using a single pipe also improves the overall structural integrity of the cooler set. With fewer welds, the risk of weak points or potential failure due to weld-related issues, such as cracking or corrosion, is minimized. This contributes to a more robust and reliable cooling unit capable of withstanding the demanding conditions of subsea environments.

[0022] Additionally, this approach simplifies quality control during production, as there are fewer welds to inspect and fewer opportunities for defects to occur. The manufacturing process is not only faster but also more cost-effective, as it reduces material waste and the need for skilled welding labor.

[0023] Overall, constructing the cooler set from a single pipe or a set of modules with straight sections and U-bend sections enhances production efficiency, improves the durability and reliability of the unit, and lowers manufacturing costs, making it an advantageous design choice for subsea cooling systems.

[0024] It should be emphasized that the term “comprises / comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does notpreclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0025] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the claimed invention.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above, as well as additional objects, features and advantages of the present invention, will be better understood through the following illustrative and non-limiting detailed description of exemplary embodiments of the present invention, wherein:

[0028] Figure 1 is a sideview of a prior art passive subsea cooler.

[0029] Figure 2 is sideview of an embodiment of a passive subsea cooler according to the present disclosure.

[0030] Figure 3 is a perspective view of the passive subsea cooler in figure 2.

[0031] Figure 4 is a perspective view of a set of passive subsea coolers as shown in figures 2 and 3.

[0032] Figure 5 is an enlarged perspective view of a portion of the top of a passive subsea cooler as shown in figures 2-4.

[0033] Figures 6a and 6b show partially the cross sections of a prior art passive subsea cooler in relation to passive subsea cooler of the present disclosure.

[0034] DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

[0035] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided forthoroughness and completeness. Like reference character refer to like elements throughout the description.

[0036] Referring to Figure 1, a prior art passive subsea cooler is depicted. The subsea cooler comprises a first header pipe, designated as 21, and a second header pipe, identified as 22. The longitudinal axis of the second header pipe 22 is substantially parallel to that of the first header pipe 21 and is positioned at a defined distance from it. Connecting these header pipes are at least one set of cooler coils, labeled as 23. These cooler coils are arranged to facilitate heat exchange by allowing a working fluid to circulate through them, effectively transferring heat to the surrounding subsea environment. The described configuration exemplifies the structural and functional elements characteristic of conventional passive subsea coolers used in various underwater applications.

[0037] Turning to Figure 2, an embodiment of a passive subsea cooler, generally designated as 1 , according to the present disclosure, is illustrated. The subsea cooler 1 includes an inlet manifold and an outlet manifold, with at least one set of cooler pipes, labeled as 2, arranged between the inlet and outlet header manifolds. This configuration facilitates efficient heat exchange by directing the flow of fluid through the cooler pipes, enabling thermal energy dissipation into the surrounding subsea environment.

[0038] The inlet manifold is composed of a first inlet header pipe, identified as 3, and a second inlet header pipe, designated as 4. These header pipes are arranged substantially parallel to one another and maintain an essentially horizontal orientation. Multiple sets of cooler pipes 2, as further detailed in Figure 3, are connected to the first and second inlet header pipes 3 and 4, respectively. That is, each of the first and second inlet header pipes 3, 4 is individually connected to a plurality of said sets of cooler pipes 2. The connection between the cooler pipes and the inlet header pipes is usually achieved through welding, ensuring robust mechanical integrity and leak-proof operation under subsea conditions.

[0039] Similarly, the outlet manifold comprises a first outlet header pipe, denoted as 5, and a second outlet header pipe, identified as 6. The sets of cooler pipes 2 are connected to these outlet header pipes 5, 6. The outlet header pipes 5 and 6 are also arranged substantially parallel to one another and aligned horizontally, mirroring the configuration of the inlet header pipes.

[0040] As depicted more clearly in Figure 3, the sets of cooler pipes 2 are arranged within a single plane, optimizing the design for both thermal performance and spatial efficiency. Each of theheader pipes 3, 4, 5, 6 is elongated, straight, and precisely aligned to ensure smooth fluid flow and efficient heat dissipation.

[0041] This embodiment exemplifies the innovative features of the present disclosure, combining structural simplicity with effective performance to address the demands of subsea cooling applications.

[0042] Figure 4 illustrates an example of a configuration where four individual units, each designated as 1 and constructed in accordance with the design shown in Figure 3, are interconnected to form a larger passive subsea cooler assembly. This modular arrangement enables scalability to meet higher cooling demands by combining multiple units into a single integrated system. The layout allows for enhanced thermal performance while maintaining structural efficiency, making it well-suited for applications requiring substantial heat dissipation in subsea environments. As can be seen in the perspective view of Figure 4, each cooler unit 1 is constructed in a modular fashion. The cooler pipes 2 are arranged in sets connected to both a front side and a back side of the first and second inlet header pipes 3, 4. This arrangement, where each header pipe serves distinct sets of cooler pipes on opposite sides, results in the multiple sets of cooler pipes being connected to each individual header pipe, which is a key aspect for achieving the high packing density and compact footprint of the cooler.

[0043] Turning to Figure 5, the arrangement of the cooler pipes 2 is depicted in more detail. In this example, the cooler pipes originating from the second inlet header pipe 4 are positioned to form the topmost layer of straight sections. Directly beneath this top layer, cooler pipes connected to the first inlet header pipe 3 are arranged to create a sublevel of straight sections. This alternating arrangement continues progressively downwards through the structure, resulting in a stacked configuration. The cooler pipes alternate between those connected to the second inlet header pipe 4 and those connected to the first inlet header pipe 3, extending through the outlet headers in a similar alternating pattern.

[0044] This tiered design ensures efficient use of space while maximizing the surface area available for heat exchange. By alternating the layers of cooler pipes associated with the first and second inlet headers, the system achieves a balanced and uniform distribution of fluid flow and thermal dissipation. Additionally, the vertical stacking of the cooler pipe layers contributes to the compact footprint of the cooler while maintaining optimal cooling efficiency.Such a configuration not only facilitates seamless integration of multiple units into a larger assembly but also highlights the adaptability of the design to accommodate diverse operational requirements in subsea environments. This innovative approach exemplifies the modular and efficient characteristics of the passive subsea cooler disclosed herein.

[0045] Figure 6a illustrates a partial cross-section of a prior art subsea cooler, the cooler pipes, labeled as 23. This design represents the traditional approach to subsea coolers, characterized by larger pipe diameters and a relatively complex assembly. In contrast, figure 6b presents the cross-section of a cooler constructed according to the present disclosure, utilizing cooler pipes with a reduced diameter. The overlay of the two cross-sections clearly highlights the differences between the prior art and the innovative design disclosed herein.

[0046] The present design achieves significant improvements over conventional systems.

[0047] Despite the reductions in pipe diameter, piping length, and overall weight, the cooling power of the system remains unchanged. Additionally, the design’s physical footprint is reduced by approximately 50%, making it a more compact and efficient solution for subsea cooling applications.

[0048] The smaller diameter of the cooler pipes not only contributes to the compactness of the design but also allows the pipes to be fabricated from single continuous sections. This eliminates the need for most of the welding required in traditional designs. By removing the numerous elbows and drastically reducing the number of welds, the present design minimizes potential failure points, improves structural integrity, and reduces manufacturing complexity and cost.

[0049] This innovative approach to subsea cooler design demonstrates a significant advancement in both efficiency and practicality, providing a robust, space-saving, and cost-effective alternative to conventional systems.

[0050] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.The terms “essentially parallel” and “essentially horizontal” as used herein are intended to describe a general geometric arrangement while allowing for minor and functionally insignificant deviations. For example, such deviations may arise from standard manufacturing tolerances or a slight inclination designed to facilitate drainage of the fluid within the pipes. These terms are therefore not limited to a strict, mathematically perfect orientation but are to be understood in the practical context of a large-scale engineered structure as would be apparent to a person skilled in the art.

[0051] While an embodiment of the present invention has been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the appended claims. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used.

[0052] The indefinite articles "a" and "an," as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean "at least one." The phrase "and / or," as used herein in the specification and in the claims, should be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.

Claims

CLAIMS1. A passive subsea cooler (1 ) comprising an inlet manifold and an outlet manifold, wherein at least one set of cooler pipes (2) are arranged between the inlet and outlet manifolds,c h a ra c t e r i z e d i nthat the inlet manifold comprises at least a first inlet header pipe (3) and a second inlet header pipe (4), wherein at least one set of cooler pipes (2) is connected to the first and second inlet header pipes (3, 4), respectively, the first and second inlet header pipes (3, 4) being arranged essentially parallel to one another and essentially horizontal.

2. The passive subsea cooler (1 ) according to claim 1 , wherein cooler pipes (2) originating from one inlet header pipe (4) are positioned to form a topmost layer of straight sections, wherein directly beneath this topmost layer, cooler pipes (2) connected to the other inlet header pipe (3) are arranged to create a sublevel of straight sections, wherein said layers of cooler pipes (2) are arranged to continue progressively downwards such that they form a stacked configuration.

3. The passive subsea cooler (1) according to claim 1 or 2, wherein multiple sets of cooler pipes (2) are connected to the first and second inlet header pipes (3, 4), respectively.4 The passive subsea cooler (1 ) according to any of the preceding claims, wherein the cooler pipes (2) are arranged in sets connected to both a front side and a back side of the first and second inlet header pipes (3, 4).

5. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the cooler pipes (2) are connected to the header pipes (3, 4) by welding.

6. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the outlet manifold comprises at least a first outlet header pipe (5) and a second outlet header pipe (6).

7. The passive subsea cooler (1) according to claim 6, wherein the inlet header pipes (3, 4) and outlet header pipes (5, 6) are arranged essentially parallel to one another and essentially horizontal.

8. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the at least one set of cooler pipes (2) is arranged in one plane.

9. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the at least one set of cooler pipes (2) comprises at least three straight pipe sections (7) and at least two 180 degrees bend sections (8).

10. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the at least one set of cooler pipes (2) is made from one single pipe.

11. The passive subsea cooler (1 ) according to claim 6, wherein the inlet header pipes (3, 4) and the outlet header pipes (5, 6) are constructed with corresponding dimensions and specifications.

12. The passive subsea cooler (1 ) according to any of the preceding claims, wherein the cooler is a modular unit, and wherein a plurality of said modular units are interconnected to form a larger cooler assembly.

Images